Industrial shredding equipment typically is used to break large objects into smaller pieces that can be more readily processed. Commercially available shredders range in size from those that shred materials like sugar cane, rocks, clay, rubber (e.g., car tires), wood, and paper to larger shredding systems that are capable of shredding scrap metal, automobiles, automobile body parts, and the like.
FIG. 1 schematically illustrates an exemplary industrial shredding system 10a. As an example only, the system is shown shredding sugar cane. Shredding system 10a includes a material intake 12a (such as conveyor) that introduces material 14a to be shredded to a shredding chamber 16a. The material 14a to be shredded may be of any desired size or shape. The material 14a is optionally pretreated, such as by heating, cooling, crushing, baling, etc. before being introduced into the shredding chamber 16a. The material intake 12a may optionally include levelers 11a, feed rollers 13a, or other machinery to facilitate feeding material 14a to chamber 16a, and/or to control the rate at which material 14a enters chamber 16a, and/or to prevent the material 14a from moving backward on the conveyor 12a. 
Because there are a wide variety of applications for shredding machines, from sugar cane processing to automobile shredding, there is a wide range and variety of shredder configurations. As examples, there are generally two types of shredders for processing sugar cane: vertical shredders and horizontal shredders. In a vertical shredder (FIG. 1), knives 15a may be used to initially break up the sugar cane so that the material is the appropriate size for the shredding process. A rotary shredding head 18a spins with a direction of rotation indicated by arrow 27a that is in-line with the direction of rotation of the conveyor 12a. Rotary shredding head 18a is configured to rotate about a shaft or axis 20a, and is equipped with a plurality of shredder hammers 22a to impact the sugar cane against a hardened surface 24a to break the material apart. The hardened surface may be, for example, the feed roller, an anvil, a grate, chamber walls, or adjacent hammers. In the illustrated example, hammers 22a work in cooperation primarily with chamber walls and grates. The rotary shredding head may have, for example, 50 to 200 hammers to break up the material. Each shredder hammer 22a is independently pivotally mounted to the rotary shredding head 18a with a mounting pin 26a (FIGS. 3 and 4). In response to centrifugal forces as shredding head 18a rotates, each hammer extends outward, tending toward a position where the center of gravity of each hammer is spaced outward as far as possible from rotation axis 20a when no material is in the chamber. The shredding chamber 16a may have one or more additional rotary shredding heads 18a to further break up the material. The shredded material may then be discharged onto another conveyor for transportation to further processing.
FIG. 2 shows one example of a horizontal shredder. In this embodiment of a horizontal shredder, a rotary shredding head 18b spins with a direction of rotation indicated by arrow 27b. Similar to the vertical shredder the horizontal shredder is equipped with a rotary shredding head 18b that is configured to rotate about a shaft or axis 20b, and is equipped with a plurality of shredder hammers 22b to impact the sugar cane against a hardened surface 24b to break the material apart. The shredded material may then be discharged onto the same conveyor for transportation to further processing. Alternatively, the material may be discharged onto a separate conveyor as disclosed in US Patent Application 2008/0277514.
Shredder hammers are routinely exposed to extremely harsh conditions of use, and typically are constructed from especially durable materials, such as hardened steel materials, such as low alloy steel or high manganese alloy content steel.
Each shredder hammer may weigh, for example, between 50 and 1200 lbs. During typical shredder operations these heavy hammers impact the material to be shredded at relatively high rates of speed. Even when employing hardened materials, the typical lifespan of a shredder hammer may, for example, only be a few days up to approximately 45 days. In particular, as the shredder hammer blade or impact area undergoes repeated collisions with the material to be processed, the material of the shredder hammer tends to wear away.
Once the hammers have been worn, the worn hammers must be replaced with new hammers. The hammers often cannot be replaced very easily. In some shredders, such as sugar cane shredders, the hammers are located within the shredding equipment such that they must be replaced by a human operating under limited conditions. Because of the weight of the hammers and the confined space in which the installer must be located to replace the hammers, it can be a difficult process and the installer is at risk of being injured while replacing the worn hammers.
In an attempt to minimize the weight to be handled by those working on shredders and ease the replacement of worn hammers, multiple two piece hammers have been used with varying degrees of success. For example, U.S. Pat. No. 2,397,776 (US '776) discloses a two piece hammer with two shanks that are rotated into a replaceable tip. However, the two piece hammer in US '776 requires the entire hammer to be disassembled in order to replace the tip. Needing to disassemble each hammer to replace the tips increases the downtime of the material reducing machine. U.S. Pat. No. 3,367,585 (US '585) discloses another example of a two piece hammer. In US '585 the replaceable tip is slid onto the shank and a pin passes through the tip and shank. Once the pin has been welded to the replaceable tip, the tip is maintained on the shank. Welding a pin onto the replaceable tip increases downtime of the equipment as the weld must be removed and a new weld put in place each time a tip is replaced. In addition it can increase the potential danger to the installer if the welding equipment needs to be used in confined spaces.
It should be appreciated that the greater throughput that the shredding equipment can process, the more efficiently and profitably the equipment can operate (i.e., minimal downtime for the shredding machine is desired). Accordingly, there is room in the art for improvements in the structure and construction of two piece shredder hammers and the machinery and systems utilizing such hammers.
Examples of shredder hammers and industrial shredding equipment are disclosed in U.S. Pat. No. RE14865, U.S. Pat. Nos. 1,281,829, 1,301,316, 2,331,597, 2,467,865, 3,025,067, 3,225,803, 4,049,202, 4,083,502, 4,310,125, 4,373,679, 6,102,312 and 7,325,761. The disclosures of these and all other publications referenced herein are incorporated by reference in their entirety for all purposes.